“The actual distribution of the centers of wheat and rice production in the world can be seen to coincide fairly accurately with the areas of adequate rainfall. A temperate climate and rainfall adequate to the production of either wheat or rice provide the agricultural basis for the power of any state. A region which lacks these elements in any appreciable degree finds itself doomed to play a secondary role in the power relations of the world.”

— Spykman, Nicholas John. The Geography of the Peace. New York: Harcourt, Brace and Company, 1944.